Rotary gear pump



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lPatented 8, 1927.* v 1 UNITED STATES FRANK w. KENNEDY, 0E- rRENroN, NEW` JERSEY, AssIeNoR 'ro DE Laver. STEAM- 'PATENT OFFICE.

TUBBINE COMPANY, OF TRENTON, NEW JERSEY, A CORPORATION 0F NEW JEBSEY- ROTARY GEAR PUMP.

Application led .Tune 11, 1924-. Serial No. 71493237. l

This invention relates to arotary pump ,I

of the gear ltype, and is moreespecially adapted, but not limited, .to a pump having helical teeth with single helix. The object of the invention is to provide means to automatically balance the end` thrust and prevent metallic contact between the ends of may not e exactly equal, and consequentlyu end thrust will result from Ithis cause also.

.Such end thrust, from whatever cause `or causes produced, causes the gears to rub against the casing, producing wear.

In my invention, forces tending to produce end thrust are-automatically counteracted and the pressures acting on oppositev ends of the gears are maintained equal.

Further, a tlm of liquid is automatically provided between the ends of the gears and the casing. There can, therefore, be no metallic contact between the ends of th gears and the-casing.

One embodiment of the invention is shown 'in the drawings, in which- 'y Fig. 1 is a sectional view through the pump. Fig.b2 is' a sideview of the pump.

The casing a is shaped to'acbmmodate the helical gears b, b', their shafts c, and

shaft bearings d. The shaft of one of the gears (b) constitutes the drivin shaft of the pump and extends through t e casing. That part of the casing enclosing the gears is of somewhat greater internal length than f the gears, leaving clearances e between the `ends of the gears and the casing.' The gears -are provided with central end recesses f l slightlyv beyond' the bearings d to the clearances e.

whose peripheriesextend There are also slight clearances g between the shafts c `and their surrounding bearings.

Communicating witl1.thedischarge side of the pump is a pipe It with branches communicating with the spaces at the ends ofthe shafts communicating with the clearances g.

The" pressure at the discharge side of the pump being greater than that a't the suction side y, there will be aiow of liquid through I thef pipe la, clearances g, recesses f and clearances e to the spaces between the gear teeth, which,'throughout an arc of each gear, open into the suction side of the pump.

Assuming that the gear b has a thrust in the direction of the arrow, Fig. l, it will, of course, have a tendency to move inthat direction, thus tending to close the escape ot'- liquid from the recess f at the right hand end of the gear and at the same time increasing the ow of liquid from the recess f at the left hand end of the gear. This results inan increase of pressure in the recess f-at the right hand end of the gear and a decrease of pressure in the recess f at the .Y

left hand lend of the gear This builds up an end pressure'tendingto move the gear froml right to'left until the forces tending i to move the gear from left to right are 4"exactly counterbalanced.- -In `other words,

perfectly balanced for end clearance area at e between the end of the l gear and the casing when the gear isin its extreme position. In other words, if it be assumed that the gear has moved to itsV .extreme right, the ressure in the left hand recess f would be t e mean between suction and discharge pressures, due to the fact that the liquid can escape from this recess faster than it can `ent/er; and the pressure in the right hand recess f would be equal to the discharge pressure. The difference in pressures on opposite ends of the gear existing in this assumed position would be substantially greater than that required to`counteract the end thrust tending to move the gear tothe right, so that infact the gear never reaches thls extreme position, and the maintenance of a film of liquid between both ends gear and the casing-is insured.

Having now fully described myA inven- Letters Patent is:

-1. A pump having a casing with an inlet of the tion, what I claiin anddesire to protect by the gears by the flow of such fluid.

2. A pump having a casing with an inlet and a discharge outlet for the fluid to be pumped, intermeshing pump gears in the casing between the inlet and discharge sides of the casing, there being a slight clearance space between the ends of the gears and the walls of the casing, there also being fluid deliver)7 conduits for delivering fluid from the discharge side of the pump to the clearance spaces between the ends of the gears and the casing, the area of the clearance space between the ends of the gears and the casing at one side of the pump being greater than the area of the inlet for the uid thereto, when the end thrust on the gears has shifted said gears from their central position and reduced the clearance space between the gears and the casing to a pre determined area at the end of the pump toward which they have been shifted, where-fby the fluid pressure at one side of the pump is reduced while the fluid pressure at the other side is maintained to counterbalance said end thrust of the gears.

3. A pump having a casing with an inlet and a discharge outlet for the fluid to be pumped, intermeshing pump gears in the casing between the outlet and discharge side of the casing, a shaft on each end of each gear extending into bearings closed at their outer ends, fluid conduits connecting each bearing with the discharge side of the pump, there being a fluid chamber between each end of each gear and the casing surrounding the shaft, a narrow clearance space between each end of each gear and the casing colnmunicating with said last mentioned chambers and the space in the casing surrounding the gears, there also being a small clearance space between the shafts and the bearings, to permit the flow of fluid from the discharge side of the pump, through the bearings, chambers and clearance spaces between the gears and walls of the casing back to the space in the casing surrounding the gears, the area of the clearance spaces between the gears and the casing being greater at one end of the gears than the area of the spaces between the shafts and bearings at said ends, when the gears are shifted toward f the other side of the casing, whereby the Huid pressure between said gears and the casing at said rst mentioned, ends of the gears is below the fluid pressure at the other ends of the gears to counterbalance the end thrust on the gears.

In testimony of which invention, I have hereunto set my hand, at Trenton, on this 7th day of May, 1924.

FRANK W. KENNEDY. 

